java - JavaFX Thread Freezing GUI -

i'm still new threading, , i'm working javafx first time, double whammy! main issue threading, believe. wanting crossfade 2 mediaplayer audios on skip button. so, believe created thread crossfade audios on 2 seconds, , should end thread. that's "think" i'm doing. however, when program runs, freezes after second skip. of code i'm using javafx tutorials , works intended before tried crossfade. advice put great use, tia! crossfade class:

import javafx.scene.media.mediaplayer; public class crossfade extends thread { private mediaplayer mp1; private mediaplayer mp2; private double currentvol;  public crossfade(mediaplayer mp1, mediaplayer mp2) {     this.mp1 = mp1;     this.mp2 = mp2;     currentvol = mp1.getvolume();     system.out.println("vol: " + currentvol); }  @override public void run() {      mp2.setvolume(0);     mp2.play();      //20 increments in volume, every 100ms     (int = 0; < 20; ++)     {            mp1.setvolume(mp1.getvolume()-currentvol/20);            mp2.setvolume(mp2.getvolume()+currentvol/20);             try            {                //sleep 100 ms                thread.sleep(100);            }            catch (interruptedexception e)            {                system.out.println("unable sleep on xfade");                e.printstacktrace();            }     }     mp1.stop();     //this.interrupt(); }  } 

audio class:

import javafx.scene.media.mediaplayer; public class audio{ public static void crossfade(mediaplayer mp1, mediaplayer mp2) {     thread xfade = new thread(new crossfade(mp1,mp2));     xfade.start(); } } 

code skip button:

skip.setonaction(new eventhandler<actionevent>() {   @override public void handle(actionevent actionevent) {     final mediaplayer curplayer = mediaview.getmediaplayer();     mediaplayer nextplayer = players.get((players.indexof(curplayer) + 1) % players.size());     mediaview.setmediaplayer(nextplayer);     curplayer.currenttimeproperty().removelistener(progresschangelistener);      //calls crossfade in audio class (supposed start thread)     audio.crossfade(curplayer,nextplayer);     //these "old" stop , play calls media     //curplayer.stop();     //nextplayer.play();   } }); 

in general, shouldn't change that's part of ui outside fx application thread. haven't worked mediaplayers, believe play same rules.

you can simplify lot using animation api. pausetransition can used manage each pause, , can "play" these in sequence using sequentialtransition. manage threading you. (this not tested...)

public class audio{ public static void crossfade(mediaplayer mp1, mediaplayer mp2) {     double currentvol = mp1.getvolume();     mp2.setvolume(0);     mp2.play();     sequentialtransition crossfade = new sequentialtransition();     (int i=0; i<20 i++) {         pausetransition pause = new pausetransition(duration.millis(100));         pause.setonfinished(event -> {                mp1.setvolume(mp1.getvolume()-currentvol/20);                mp2.setvolume(mp2.getvolume()+currentvol/20);         });         crossfade.getchildren().add(pause);     }     crossfade.setonfinished(event -> mp1.stop());     crossfade.play(); } } 

of course, if you're going use animation api, may use in way "smoothly", instead of in discrete steps:

public class audio { public static void crossfade(mediaplayer mp1, mediaplayer mp2) {     final double currentvolume = mp1.getvolume();     mp2.setvolume(0);     mp2.play();     timeline crossfade = new timeline(new keyframe(duration.seconds(2),              new keyvalue(mp1.volumeproperty(), 0),              new keyvalue(mp2.volumeproperty(), currentvolume)));     crossfade.setonfinished(event -> mp1.stop());     crossfade.play(); } } 

update: if still using javafx 2.2, replace lambda expression (crossfade.setonfinished(event -> mp1.stop());) inner class:

crossfade.setonfinished(new eventhandler<actionevent>() {     @override     public void handle(actionevent event) {         mp1.stop();     } }); 

you need declare mp1 final:

public static void crossfade(final mediaplayer mp1, final mediaplayer mp2) { ... }